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Thanks to all of you ..... and all those different answers!!    Here goes:

4 said corn flour was maize starch
4  -  masa harina
10  - for cornstarch
4 -  for a very finely ground corn meal
100% corn flour can be purchased at Authentic foods, or at the
   glutenfreemall.com

........ Guess the winner is cornstarch.

Caster sugar came in with about three different answers, and the most votes
were for an extra fine sugar....at least according to about 10 people.   Two
said it was regular sugar, and a few mentioned confectioner's sugar.

Thanx again!   Meanwhile, the OTHER chocolate cake came out pretty
good!!  Bev Mansfield, Oh